I think music actually does have an evolutionary purpose because of a few reasons....
1. We can use sounds to alert people or transmit messages, i.e. the way that Morse Code developed and used specific dot patterns to transmit a message. It's based on the same general idea of using unique sounds to share information.
2. Can be used to have fun! For some unknown reason, we have the ability to think pretty deeply about the world around us. We have urges beyond just eating, sleeping, using the bathroom, etc. We want to play! So music is a way that the brain can actually "exercise" itself and play by coming up with new sounds.
3. From a social perspective, music bonds people: I can bet you that there are people out there with political beliefs that make you shudder and yet you both have a few bands/artists in common that you love to listen to. Music's this weird place of a stalemate between people because it unites them together to listen to something cool. It's an easy conversation starter, too, because music emotionally resonates with us and we like to talk about why.
4. Music helps with remembering information, most likely because of those emotional links I mentioned. A song can bring you back to a moment in such vivid detail!
What do you all think?